Kotlin 1.8 support

[ZacSweers]

• Deprecate KotlinCompilation.singleModule option as it no longer exists in kotlinc.
• Propagate @ExperimentalCompilerApi annotations
• KotlinJsCompilation.irOnly and KotlinJsCompilation.irProduceJs now default to true and are the only supported options.
• Expose new KotlinCompilation.compilerPluginRegistrars property for adding CompilerPluginRegistrar instances (the new entrypoint API for compiler plugins)

  KotlinCompilation().apply {
    compilerPluginRegistrars = listOf(MyCompilerPluginRegistrar())
  }

• Deprecate KotlinCompilation.compilerPlugins in favor of KotlinCompilation.componentRegistrars. The latter is also deprecated, but this is at least a clearer name.

  KotlinCompilation().apply {
  -  compilerPlugins = listOf(MyComponentRegistrar())
  +  componentRegistrars = listOf(MyComponentRegistrar())
  }

• Don't try to set removed kotlinc args. If they're removed, they're removed forever. This library will just track latest kotlin releases with its own.

[ZacSweers]

I've published 0.1.0-1.8.0-Beta01 at this point in the PR's changes on maven central